Israel launched an unprecedented wave of strikes at Iran last week, to which Tehran responded with missile and drone attacks.

Moscow is one of Iran's most important allies, with the two deepening military cooperation and inking a strategic partnership agreement just months ago.

But the Kremlin has not provided military support to Iran in the face of Israeli air strikes, and President Vladimir Putin is pitching himself as a possible mediator even as he condemns Israel.

"We would like to particularly warn Washington against military intervention in the situation," Russian foreign ministry's spokeswoman Maria Zakharova told reporters.

US President Donald Trump had said Wednesday he was considering join Israel's strikes on Iran.

"I may do it, I may not do it," he said.

He also rejected Russia's offer to broker peace, saying he told Putin to resolve the Ukraine conflict first.

Kremlin spokesman Dmitry Peskov said Thursday that it was not up to Trump to reject Putin's offer.

"These services can be accepted by countries that are currently directly involved in the conflict," he said.

- 'Not asked' -

Zakharova warned any US military action "would be an extremely dangerous step with truly unpredictable negative consequences".

Moscow issued its warning after Putin spoke with his Chinese counterpart Xi Jinping, with the pair blasting Israel.

Putin and Xi "strongly condemn Israel's actions," the Kremlin said after the call.

Putin aide Yuri Ushakov told reporters that Moscow and Beijing believed the end to the hostilities "should be achieved exclusively by political and diplomatic means".

Russia has for years been a key actor in the Middle East, managing to maintain warm relations with all major players in the region.

But the fall of key ally Bashar al-Assad in Syria last year, and Israel's war in Gaza -- which Putin has repeatedly raised concerns about -- have threatened to dent that position.

Despite their close military ties, Putin said Iran had not requested military help in the week since Israel launched its attacks.

"Our Iranian friends have not asked us about this," Putin said in response to a question from an AFP reporter at a late-night televised press conference in Saint Petersburg.

He also pointed out that the treaty signed in January was not a mutual defence pact and did not oblige either side to provide arms or assistance.

Asked what steps Russia would take if Iran's supreme leader Ayatollah Ali Khamenei was assassinated, Putin said: "I don't even want to discuss such a possibility."

His spokesman said later Thursday that Russia would be prepared to send humanitarian aid, if requested to by Tehran.

- 'Mediate your own' -

In their phone call, Xi told Putin that a ceasefire was "top priority" and also criticised Israel.

"Promoting a ceasefire and cessation of hostilities is the top priority. Armed force is not the correct way to resolve international disputes," Xi said, according to China's state news agency Xinhua.

"Parties to the conflict, especially Israel, should cease hostilities as soon as possible to prevent a cyclical escalation and resolutely avoid the spillover of the war," he added.

Last week, Putin held phone calls with Israeli Prime Minister Benjamin Netanyahu and Iranian President Masoud Pezeshkian, offering himself as a peacemaker.

The Kremlin said that Xi had spoken "in favour of such mediation, since he believes that it could serve to de-escalate the current situation", Ushakov said.

But Western leaders, including Trump and France's Emmanuel Macron have pushed back against the idea of Putin trying to mediate the conflict amid his own Ukraine offensive.

"He actually offered to help mediate, I said: 'do me a favour, mediate your own'," Trump told reporters on Wednesday about Putin's efforts.

"Let's mediate Russia first, okay? I said, Vladimir, let's mediate Russia first, you can worry about this later."